The Effects of Progressive Anemia on Jejunal Mucosal and Serosal Tissue Oxygenation in Pigs

Abstract

Anemia may promote intestinal hypoxia. We studied the effects of progressive isovolemic hemodilution on jejunal mucosal (Po2muc), and serosal tissue oxygen tension (Po2ser, Clark-type surface electrodes), mucosal microvascular hemoglobin oxygen saturation (Hbo2muc), and hematocrit (Hctmuc; tissue reflectance spectophotometry) in a jejunal segment. Twelve domestic pigs were anesthetized, paralyzed, and mechanically ventilated. Laparatomy was performed, arterial supply of a jejunal segment isolated, and constant pressure pump perfused. Seven animals were progressively hemodiluted to systemic hematocrits (Hctsys) of 20%, 15%, 10%, and 6%. Baseline for Po2muc, Po2ser and Hbo2muc was 23.5 +/- 2.1 mm Hg, 57.5 +/- 4 mm Hg, and 47.0% +/- 6.4% which were not different from the five controls. Despite a significant increase in jejunal blood flow, jejunal oxygen delivery decreased and oxygen extraction ratio increased significantly at Hctsys 10% and 6%. Po2ser decreased significantly below or at Hctsys of 15%, whereas Po2muc and Hbo2muc were maintained to Hctsys of 10%, but less than 10% Hbo2muc and mesenteric venous pH decreased significantly, implying that physiological limits of jejunal microvascular adaptation to severe anemia were reached. Decrease of Hctmuc was less pronounced than Hctsys. In conclusion, redistribution of jejunal blood flow and an increase in the ratio of mucosal to systemic hematocrit are the main mechanisms maintaining mucosal oxygen supply during progressive anemia.

Evaluation of Splanchnic Perfusion and Oxygenation during Positive End-Expiratory Pressure Ventilation in Relation to Subcutaneous Tissue Gases and pH

“…This good correlation between PscO 2 and PserO 2 continued throughout all PEEP levels. This is in agreement with other studies indicating very good correlation between these variables in different situations like hypoxic hypoxia [14], haemorrhage [9] and anaemia [25]. These studies also indicate that such a correlation does not exist between PscO 2 and mucosal PO 2 [13,14,25].…”

“…This is in agreement with other studies indicating very good correlation between these variables in different situations like hypoxic hypoxia [14], haemorrhage [9] and anaemia [25]. These studies also indicate that such a correlation does not exist between PscO 2 and mucosal PO 2 [13,14,25]. This is probably due to redistribution of the blood flow within the intestinal wall, in order to maintain mucosal oxygen supply [25].…”

“…These studies also indicate that such a correlation does not exist between PscO 2 and mucosal PO 2 [13,14,25]. This is probably due to redistribution of the blood flow within the intestinal wall, in order to maintain mucosal oxygen supply [25]. Serosal oxygen tension is more likely to reflect the oxygen tension of the gut wall, thus indirectly predicting anastomotic healing.…”

The effect of the transfusion of stored RBCs on intestinal microvascular oxygenation in the rat

“…As a result, the pO 2 gap, the difference between the intestinal μpO 2 and P MV O 2 that occurred during shock, persisted after transfusion of the stored RBCs. Several mechanisms have been proposed 29 to explain the discrepancy between microvascular pO 2 and regional venous pO 2 that is observed during hemorrhagic shock 18,19,30 and anemia 31 . The pO 2 gap between mesenteric venous and microvascular blood might be attributed to changes in intramural blood flow redistribution, 31–33 direct diffusion of O 2 from arterioles to venules, 34 or an inability of Hb to offload O 2 to the tissues quickly enough as it passes through the microcirculation 35 .…”

Autologous Transfusion in Children: Blood-Saving Techniques

“…Nevertheless, lactacidosis occurred in isolated cases, which leads us to assume that the absolutely critical threshold was reached. Animal experiments showed that below 10% Hct systemic and myocardial lactate production commence as a manifestation of oxygen deficiency [24,25]. Deliberate hypotension to a mean arterial pressure of 40-50 mm Hg also contributes to a decrease in intraoperative blood loss.…”